Grinding machine



A. DE LEEUW 2,099,161

GRINDING` MACHINE Filed Aug. 30, 1955v y 3 Sheets-Sheet 1 Nov. 16, 1937.

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H GRINDING MACHINE Filed Aug. 3o, 1955 ssheets-sheet 3 24 UNL 0 c/r HDMPH L DE L EEL/'w Patentedv Nov.` 1.6,.*1'937 UNITED "STATES PATENToEFlcE GRINDING MACHINE l Adolph'L. De Leeuw, Plainfield, N. J.,assigner to Norton Company. W tion of Massachusetts applicaties augustso, 193s, sensi so; sacas s claims. (ci. isi-105) '10 provide asteadyrest and mechanism associated therewith improving the operation of.a grinding machine in which the work is gripped by end J pressure ofrotating devices, the pressure being located along the axis ofcylindrical work pieces.

15 Another object of the invention is' to improve the machine disclosedin U. S. Letters Patent No. 2,059,895 dated November 3, 1936 to CharlesH. Norton and Albert G. Belden (Serial No. 566,738). Another object-ofthe invention is ilrmly to sup- 20 port a work piece underall conditionsof 'practical operation. Another object of the invention is to increasethe production of a precision grinder. Another object of the inventionis to improve the machine -of U. S. Letters Patent No,

25 1,779,779 to Charles H. Norton. -Other objects i will bein partobvious or .in part pointed out hereinafter. r

The invention accordingly consists in the features of construction,combinations of elements.

' 30 and arrangements of parts as'will be exemplified in the structureto be hereinafter described, and the scope of the application of whichwill be indicated inthe following claims.

. In the accompanying drawings, in which is 35 shown rone of variouspossible embodiments of the mechanical features of this invention,

Fig.l 1 is a transverse sectional view'through a grinding machineembodying the invention par- 40 ticularly illustrating the crossfeed-for the grind# ing wheel and the' steadyrest feeding mechanism,Fig. 2 is an enlarged fragmentary sectional `view of a switch, thesection being taken on the line 2-2 of Fig. 1, 45 Fig. 3 is afragmentary elevation of a load and fire vdevice and clutch,

Fig. 4 is a sectional view taken on the line l-I of Fig. 3, y

5 dos Fig. 6 is an enlarged sectional view of of the transmission, thesection being taken along Fig. 5 is a perspective view of anactuatinglng wheel, work piece and including theisteadyrest slides, I

Fig. 8 is an enlarged vertical sectional view of another` part of thetransmission also of the steadyrest slides, the section being takenalong 5 the line 8-8 of Fig. 1,

Fig, 9 is a vertical sectional view of part .of the tron mechanism, thesection beingtaken along the line 9-9 of Fig. 6.

First referring to Fig. 1, I provide a machinev 1o L;

base 20 which should be massive venough to hold 'the various machineelements rigidly enough to obtain precision results but may be hollowand provide mechanism supporting compartments,

the shape thereof in a particular embodiment of this invention bell-'lg`clearly illustrated lin the drawings wherefor I shall not furtherdescribe the same in detail. Uprising from the base is a pair of heads2l, one of which is shown inv Fig. 1 and both of which are indicated insection 20 in Fig. 7;- these heads as more particularly shown in Fig. 7support bearings 22 for hollow spindles 23 supporting tapered spindles24 having disk shaped heads 25; resilient means, not shown.

urges the spindles 23 towards each other in order 25.

to grip work pieces W, one embodiment of such means together with power`means for opening and closing the work holding orchuckingniechanismbeing disclosed in U. S; Letters Eat'ntNo.

1,779,779 to Charles I-I. Norton, to which reference may be had.l Themachine thus provides a work holding mechanism to hold a work piece W byend contact and 'pressure in an axial direction, and one or both of thespindles 23 may be `driven to rotate the work piece W. I prefer to driveboth spindles 23 in so much as thereby a superior drive is eifected, andthe driving mechanism may be of the type shown in the aforesaidNortonpatent, or it may be of any other suitable type. The taperedspindles 2l 40 are removable and a number of them may be provided forvarioua sizes and shapes of work pieces to be operated upon.

Referring now to Fig. 1, Iprovide a grinding wheel mountedfupon aspindle 3| which may 45 be journaled and driven in any usual or desiredmanner, and in accordance with established practice I rotate the wheel30 in the direction of I prefer to rotate the' work piece vv in theoppowe,

site vangular direction to that of the grinding wheel 30,v so that atthe line of contact their surfaces are moving in the same direction,although at different velocities. I may cause the relative surfacevelocity between wheel and work piece to be highly eiiicient for aparticular size Vof work piece and a particular grade of wheel byrotatingthe grinding wheel 30 at a somewhat higher speed than if thewheel and work piece rotated inthe same angular direction, all Withinthe limits of practical requirements, and by this arrangement of thedrive the wheel tends to rotate the work so that there is less chance ofslippage between the work and the disks 25.

I mount the spindle 3| in la spindle head 32 part of which is shown inFig. 1, and which may be integral with or suitably attached to a crossslide 33. Referring now more particularly to Fig. 6, the cross slide 33has plane and V-vsurfaces 34 and 35 on its under sidewhich rest uponplane and V-surfaces in ways 36 and 31 which are attached to the machinebase 20 and mount the wheel head 32 and the grinding wheel 30 formovement transverse to the axis of the work piece W. As shown inFigs. 1. and 6 I provide a screw 40 which, in this embodiment of theinvention, is the medium of transmittal of rall movements ofthe slide 33on the ways 36 and 31, both for feeding and adjustment.I The screw 40 ismounted in radial bearings 4| and 42 and it abuts thrust members 43 and44, the thrust member 43 being inserted in a bore provided by the slide33, as shown in Fig. 1, and the thrust member 44 being adjustable in aninternally screw threaded member 45'which is located in the bore in theslide 33 vand fastened thereto. The screw shaft40 has a reduced portionwhich extends through the thrust member 44 and is vfastened to a gear41` which meshes with a gear f base20 which actuates the powertransverse feed and the power feed for the' steadyrest, and may rotatethe work piece if desired. The armature shaft 56 has fastened thereto aclutch e1ement'51`, there being a mating clutch element 58 keyed to ashaft 59 which is mounted in bearing blocks 60 and 6| provided in themachine frame 20. The clutch element 58 is urged to the right in Fig. 6by means of Va spring 62 backed up by a collar *63, and a yoke lever 64pivoted at 65 in a bracket 66 will move the clutch member 58 out ofengagement with the clutch member 51 to disconnect the drive when theyokelever 64 is moved by the core 61 of a solenoid 68, which core 61 isconnected to the lever 64 by a link 69. `Fig. 6 shows the solenoid l68energized and the clutch disconnected, but as soon as the solenoid 68 isdeenergized thec spring 62 reconnects the clutch.

Referring now to Figs. 6 and 9,-the shaft 59 has fastened thereto a wormgear 10 which meshesv with a worm wheel 1| fastened to a shaft 12mounted inbearings 13 and 14 provided in a gear casing .15 which ismounted inthe machine base 20. Secured to a shaft 12 are spur .gears 16and 11 which constantly mesh with spur r limiting stops theregears 18and 19. The gear 16 lis small and the gear 18 relatively large, whilethe proportions of the gears 11 and 19 are different, with the result"that the gear 18 is rotated at a slow speed while the gear 19 is rotatedat a higher speed; gear 18 is fastened to a sleeve 80 mounted inajournal 8| provided in the gear casing 15 while gear 19 is mounted onbut not fastened to a shaft 82 journaled in a journal 83 provided in thegear casing 15 andalso in the sleeve 80. Shaft 82 has keyed thereto adouble clutch element 84 having a groove for the reception of a shiftingyoke 85; one end of the clutch member 84 may be brought into engagementwith a clutch element 86 integral with the gear 19, while the other endof the clutch member 84 may be brought into engagement with a clutchelement 81 integral with the sleeve 80, the clutch member 84 beingslidable upon the shaft 82 for the purpose of conecting either the gear18 or the gear 19 to the shaft 82 and thus driving the shaft 82 ateitherl a slow finishing feed rate or a fast cutting feed raterespectively.

Still referring to Fig. 9, fast upon the end of the shaft 82 is a bevelgear 90 meshing with a ubevel gear 9| fast on a shaft 92. Referring nowto Fig. 6, the shaft 92 is connected by means of a clutch 93 with ashaft 94 which is journaled in bearings 95, 96 in the machine frame. Thepurpose of the clutch 93 is to permit the gear box 15 to be removed as aunit and the shaft extends forwardly to a nut 91 for setting up ormaking 'adjustments of the machine.

Fixed upon the shaft 94 is a worm 98 which meshes with a worm wheel 99which is mounted upon and drives a shaft |00. The shaft |00 is thusrotated at a reduced speed through a transmission train involving a pairof worm and worm wheel reduction units and at the selected rate of twofeed rates, determined by the change gear mechanism described, that isto say at a rapid feed rate or at a slowor finishing cut feed rate. Theshaft |00 is lconnected to feed transversely the slide 33 and it is alsoconnected simultaneously to feed the steadyrest mechanism in timedrelation thereto. In this particular embodiment of the invention, I havedisclosed a two-rate feed mechanism and also a start and stop clutch inthe transmission train but no reversing mechanism and the retrogrademovement of the slide 33 and also the supports for the steadyrest iseffected by' barrel or ltrack cams. Certain advantages inhere in the useof such barrel or track cams among them being simplicity of operationand flexibility of control. l

Considering now the cam mechanism which drives the slide 33 and stillreferring to Fig. 1, the worm wheel 99 is fastened to a drum |0| whichhas a cylindrical surface |02 bounded by a shoulder |03 at one end andof a size to receive any one of a number of barrel or track cams |04having a cam groove |05 and keyed to the drum |0| by a key |06, it beingunderstood that for different grinding conditions and different workpieces speclcally diiferent cams |04 may be employed. The drum |0| iskeyed by means of a key |01 to the main control shaft |00. and thus itis that the worm wheel 99 drives the shaft |00.

The drum |0| is maintained upon the shaft |00 by means of a couple ofnuts |08 on a screw threaded portion of the shaft |00. .The shaft |00 isjournaled in main journals ||0 and provided in the machine base, and inorder that end play may be eliminated washers ||2 abut the journal andare backed up by a collar ||3 xed'to the shaft |00 by means of a taperpin ||4; the nuts |08, a washer ||5, the drum |0| and a pair of washersI I6 being used to eliminate end play in the other direction and toadjust and tighten the assembly.

The shaft |00 has a reduced portion ||1 upon which is fitted a bushing||8 in the central hub ||8 of a cover |20 which may be secured byscrews, not shown, to the base 20. Inside the cover andfastened by meansof screws, not shown, to the drum |0| is an actuating dog drum |2| witha pair of T-slots |22 and |23 in which may be placed at any desiredangular position dogs to actuate the control for the change gearmechanism to shift from fast to low feed.

Referring now to Fig. 6, the slideway members 36 and 31 haverespectively the opposite slidewaysurfaces and |25 of a dovetailedslideway which supports for movement, parallel to the slide 33, a slide|21. The slide |21 has secured to the top thereof a half nut |28 whichengages the screw shaft 40. Slide |21 also has, as shown in Fig. 1, astop stud |29 positioned to engage a stationary stop stud |30 located inthe machine base 20, so that the forward position of the slide l21 isxed and predetermined and never varies..

The slide |21 is moved by means of the cam drum |04 but through aresilient connection so that the stops |29 and |30 will, determine thenal position. Referring nowl to Figs. 1 and 6, the slideway- |21 hasformed on the under side thereof dovetailed slideways |31 supporting aslide |3| in the rear part of which is located a verticalstud |32 uponwhich is mounted a roller |33 fitting in the track |05 of the barrel cam|04. The'roller |33 is frusto-conical and the walls of the slot or track|05 are inclined so as to make a nice fit. Rotation of the cam |04causes a forward movement of the'slide |3| which is connected to ltheslide 21 by means of a compression spring |34 located on a bolt '|35fastened to the slide |3| and projecting through .a portion of the slide|21, as shown. When the slide |3| is moved forwardly the slide |21 moveswith it in so much as the spring |34 is compressed and by its action iturges nuts |36 on the bolt |35 against a portion of theslide |21, butwhen a positive resistance is encountered the spring |34 will compress,`the nuts |36 moving away from a front surface of the slide |21.Retrograde movement of the slide' 3| draws the slide |21 rearwardly bypositive action.

According to the invention I may determine the nal size of the workpiece by bringing the wheel slide to a fixed and predetermined positionat the same time holding the work piece against the grinding wheel bysurfaces which for the final size are located at a predeterminedposition. At the same time I may rotate the work by frictional orotherwise end contact, with pressure in an axial directiorifand byreason of such construction and mechanism, loading is a momentarymatter. Tracing the grinding operation back-V wards, in order thatchatter marks may be eliminated and adrive effectedwhichkeeps therotating spindles coaxial with the work piece, I move the steadyrestawayl rom the axis of thework piece in the opposite irection and as thwheel slide moves backwards.v I prefer to provide two work piecesupporting surfaces so that the work may be supported 'atfmor/e than twoplaces, including the-line of grinding, and I compensate for the changeof 'size of the work piece 'by moving the steadyrest at a greater ratethan the grinding wheel feed slide, which rate is determined by thecosecant of the dihedral angle between the plane through the axis of thework pice and parallel to the advance of the steadyrest and the plane oftangency of either rest with the work piece, such ldihedral angles beingpreferably the same as otherwise one steadyrest surface wouldleave thework piece or cause undue pressure between the parts at some stage ofthe operation. Thus as the angle defined becomes smaller the rate offeed of the steadyrest mechanism divided by the rate of 'feed of thefeed slide becomes` larger, until with the steadyrest surfaces tangentto the top and bottom of the work piece this ratio is infinity becauseif such a steadyrest should hold the work piece at the start of anoperation, it could never hold it after it had been ground to anyextent. By making the dihedral angle defined for the two steadyrestsurfaces the same, a single work piece cooperates with the relativerotation of Wheel and work `piece hereinbefore defined and to a largeextent reduces pressure and resistance and increases the effectivenessof the threepoint support. v

Considering now the mechanism for the movement and support ofthesteadyrest surfaces, and referring to Figs. l and 8, the shaft |00 hasmounted thereon at its front end a gear |40 whiclris keyed to the shaft|00 and which meshes with a'gear |4| mounted on a stud |42mounted 1 in asteadyrest mechanism frame unit |38 and projecting through the machinebase 20 and the gear |4| meshes `with'a gear |43 secured to a shaft |44.Shaft |44 has an enlarged portion |45 spaced by washers |46 from the endof a bearing |41 provided by the frame unit |38. The bearing |41 is botha radial and thrust bearing and at its front end there are washers |48abutting it and also the hub |49 of a drum |50 similar to the drum 0|.'Atlthe other end of the hub |49 is a washer |5| and nuts |52 the lattermounted on a threaded portion of shaft |44; the shaft |44 has a reducedportion |53 fitting in a journal |54provided in a cover member |55secured tothe frame unit |38.

Keyed to the drum is a barrel or track cam |56 having a cam'slot |51 inwhich is a roller |58 on the end of a stud |59 depending from a slideunit |60. Secured to the drum |50 is an operating or dog drumll having asingle T- slot |62. This mechanism is thus similar to the mechanism foradvancing the slide 33 but in this embodiment of the invention the throwof the cam slot |51 is double that of the cam slot |05.

Referring now to Fig. 8, there is provided a slideway having dovetailedways |56 to receive the slide |60 and having further dovetailed Ways |18for the support of the steadyrest member |19which, as shown in Fig. 7,comprises an integral rectangular slide portion integral with apairofrest arms |80, the part being Y-shaped in cross section as shown inFig. 1.

Referring now to Fig. '1, the slide |15 `is ordinarily in advancedposition, that is to say in the direction of the work piece with respectto the slide |65, being held in that position by springs |8| aroundbolts |82 which extend between standards y| 83 and |84 providedrespectively on the slide |65 and the slide |15. Nuts |85 limit theforward position of the slide |15 with respect to the slide |65. Theslide |11 is, during the grinding operation retracted with relation tothe slide |15, being held merely temporarily in the position shown inFig. '1 by a spring |86 extending between the standard |84 and astandard |81 provided on the slide |11, and there being a lbolt |88 andnuts |88 to limit the advanced position ofthe slide |11 and nuts |80 toprovide a solid backing for slide |11. Thus these three slides duringcertain parts of the operation function as one, and the operator maygrasp a knob 8| to pull the slide |11 away from the work piece 'whenloading. Likewise the springs |8| provide for relative movement betweenthe slides |65 and |15 at the ilrst part of the grinding operation tofacilitate the grinding of out-of-round Work pieces, but prior to thefinishing of the grinding` operation I* may positively move the slide|15 to its advanced position with respect to the slide |65 by amechanism which will presently be described. It maybe noted here thatfor certain operations and certain classes of work one of these slidesmay be dispensed with, and for cer.- tain operations I .prefer analtogether rigid mechanism, and I contemplate that the grinding wheeland the steadyrest shoes |82 shall hold the work piece coaxial with thedriving heads 25 especially for the final and nishing' cuts.

Considering n ow the grinding of a work piece W, and assuming that thecam drums |04 and |56 are in such angular position as to withdraw bothslides, the operator grabs the handle |9|,

Iand withdraws the slide |11 and thus the steadyrest arms |80, while atthe same time setting in operation mechanism disclosed in the patent toNorton referred to, to retract the work gripping disks 25. He may theninsert a work piece W and cause the disks 25 to\approach to grip the butthe rest shoes |82 may be allowed to engage to the shoe 203 is aninsulating plate 204 to which is secured a metal plate 205 that iscontacted by spring pressed contacts 206 and 201 in a switch box 208.wWhen the arm 202 is moved clockwise, Fig. 1, the plate 205 leavesthe'contact 201, and thus breaks a circuit between lines 209 and 2|0which, together with line 2|| energize the solenoid 68. Then when theoperator pushes the lever 200 away from him, the solenoid 68 isdeenergized,' permitting the spring 62to cause engagement of the clutchmember 58 with the.

clutch member 51 thus actuating the feeding mechanism. The drums andn|50 are thereupon rotated causing the slides ||6 and 33 to approach eachother at the relative rates hereinbefore specied, and at this time theclutch 84 is in the vposition shown in Fig. 9 to cause a rapid movement.The rate is constant, however, only so far as the angular velocity ofthe barrel cams |04 and |56 are concerned, and any desired rate orchange of rate may be incorporated in the shape of the cams; I prefer tomake the camtracks and |51 similar in pitch at a definite ratio to eachother in order that the work piece W may bev centered upon a threepointsupportI comprising .the steadyrest shoes |82 and the grinding wheel 30at all times during the grinding operation.

In Fig. 1 I have shown the steadyrest shoes |82 in contact with the workW prior to engagement of the wheel with the work piece. Until thegrinding wheel'engages the work piece, however, the shoes have no eifectupon the work piece, and in fact the principal reason for providingaseparate slide |11 and the spring |86 vis to facili- .tate centeringthe work between the disks 25, 25,

for the operator may place the work piece W tangent to the shoes |82with the slide |11 forward in order to ilnd the correct position for thework piece; vthe spring |86 is a very light spring and in certain casesthe nuts |88 may be tightened up to hold the standard |81 between themand the nuts |90.4

The slow feed comprising the gears 16 and 18 is provided to give themachine greater capabilities within the limits of a reasonable sizledlcam drum and at a predetermined but adjustable position a dog 2|2located in the T-slot |23 engages a detent 2|3 which as shown in bothFigs. 6 and 1 causes the shifting of a rod 2|4 toward the front of themachine, which rod is slidable in a bearing bracket 2 5 nxed to themachine base 20. 'I'his may happen at or after the commencement ofgrinding. Referring now to Fig. 1, a link 2|6 connects the rod 2|4 to anarm 2|1 which is fastened to a shaft 2I8 mounted in a stationary bracket2|8, which shaft 2|8 passes through and controls the yoke 85 in the gearchange box 15 in order to shift the clutch 84. Accordinglyforwardmovement of the shaft 2|4 shifts the clutch 84 to cause the transmissionto act through the fine or slow feed gearing. The grinding operationproceeds until such a time as cam slots |05 and |51 have advanced thewheel and the steadyrest tothe limit of travel, whereupon the cam slotsreverse the direction of movement and separate these parts. At thereversal of movement, the grinding is completed, and in order to savetime the pitch of the cam slots may be high for the movement ofseparation and the rapid feed may be engaged. I provide-a dog 220 toengage thev detent 2|3 and move the rod 2| 4 rearwardly to bring theparts back to initial position rapidly in order to save time, and in thepreferred embodiment of the invention the cam drums rotate 360 for eachgrinding operation and then come to a stop by reason of the engagementof a. dog 22| on the `drum |6| with a spring pressed detent 222 on theend of a rod 223 which is mounted in an yarrn` 224 integral with arm202.

As shown in Figs. 1 and 8, a spring 225 around the rod 223 actingagainst a head 226 constitutes resilient means'for maintaining thedetent in its upper position, there being a screw 221 and a- .a,oaa,1e1.Y.

.- for readily adjusting the position 1oi? anylsteady tions. -Themachine may'be started in spite of device which is especialLvillustrated in Figs. 3

the engagement of dog 22| with detent 222, because thespring 225 willcompress allowing the switch controlling the solenoid 68 to be opened;

the machine comes to a stop with the partsl in the initial position whenthev drums have ytraveled 360 and the arm '202 has been moved again to`Jreenergize the solenoid 68.

In order to avoid possible failure of the mechanlsm-by reason of theclutch 84 hangingin mid or neutral position, I provideY a load and -ilreand 4, and which comprises a pair of spaced arms 225 vconnected to theyoke 85 having adjustment may be formed to throw the dagger 231 from onenotch partiallyinto the other but without disengaging the clutch by sodoing, owing to the lost motion, whereupon the spring will carry thedagger and shaft 2|8 the-rest of the .distance -to shift the clutchmember from oney side to the other.

For, the grinding of many work pieces the mech anism and mode ofoperation which has been described may besuflicient and give the bestresults, but in certain cases I may use the springs |8| to permit thesteadyrest-to back away especially at the start'of a grinding operation.providing mechanism to lock the slides |55- and |15 in definite spacedposition automatically' before the finish ofthe grinding operation.I Itmay be understood, however, that in many respects the provision ofsimple spring means will effect this result and in certain cases Iprefer to use a steadyrest which is always maintained in geometricallycorrect position with a ilrm pressure.

Considering, however, the additional mechanism which may be used uponoccasion, (at other times the slide being pinned orrigldlyfastened tothe slide |65 and the parts particularly to be now described4 beingaltogether removed from the machine) there is a wide hole through theslide |60 permitting a screw rod 240 which passes through a boss 24| inthe center of the slide |65 to extend downwardly through the slide |60.A nut 242 is mounted onthe rod 240 and this may be locked in position bya check nut 242, which holds the rod 245 from rising above a certainposition. To the lower end of the rod 240 is fastened an arm 244 whichhas a portion 245 in position to be engaged by dogs 246 and 241 ad-VJustably secured in the T-slot `|62 of the drum |5|`. The`former dogmoves the arm I245 to lock the slide |15 to 'slide |65 in advanced xedposition, while thelatter unlocks the parts. This is effected by meansof a' wedge member -25|) having, as shown in Fig. 1, an inclined surface25| on its right hand side adapted to engage a stationary wedge 2524secured to or integralwithv 255 may be provided to lift the wedge nut250 i when the parts are unlocked.

Considering now Fig. 7, the steadyrest member |18 may be readily removedfrom its supporting slide |11 by removing bolts 250 whichiit in slots25| in thesteadyrest member |19 and screw into,y

holes inthe slide |11. This constitutes means rest with respect to itssupporting slide |11./f`

Comparing-now Figs. 6 and 8, an exampleof the timing of the machine isshown.l It should be remembered that the change of feed rate may beinaugurated either at the commencement of grinding or at some latertime; in the first inthe parts together into grinding position and inthe second instance fast feeding performs what may be called the roughgrinding. These variations 4are all within the contemplation of theinvention, being made by mere adjustments of the machine. By wayof-example only, therefore, turning to the right hand side of Eig. 8 itwill be seen that the dog 2|2, which is moving in this viewcounterclockwise, will move 120 lbefore it contacts the detent 2|`3 atwhich point the slow feed is inaugurated. For seventy-five more degreesof angular movement the grinding.

takes place at a slow feed and at the end thereof i there is practicallya dwell in the cams and as the cams commence to withdraw the' slides'the second dog 220 causes the mechanism to feed rapidly again. CompareFig. 6 with Fig. 8 remembering that direction of rotation is opposite inthese two figures.

' stance fast feeding is for the purpose of bringing Referring now 'tothe left hand side of Fig. s.

165 subsequent .to the start of an operation the slides |55 and |15 arelocked together by means of the dog 246, while the unlocking operationtakes place 45 thereafter which is 210 vfrom the start of the operationor 15 after the reversal in 'direction It must be emphasized, however,that this is only-one of a`. great many ways of setting `up the machineand is given for a clearer understanding of the mechanism. Ultimatelyafter 360 of rotation dog 22| operates the detent 222 whereupon themachine stops and is ready for another cycle of grinding.

In the of successive workpieces the grinding wheel will ultimately wear,but this can be advanced with respect tothe slide |21 by means of thehand wheel 53, and a dressing operation may be performed to bring thevertical planeo! tangency with the wheel to afixed position s o thatrigid control over the ultimate size of work pieces may be readilyachieved.

- It will thus be seen that there has been provided by this invention anapparatus in which the various objects hereinabove set forth togetherwith many thoroughly practical advantages are successfully achieved. Asmany possible embodiments may be made of the above invention and asgrinding wheel, a slide for such steadyrest, power means to advance andretract the rst named slide, power means to advance and retract thesecond named slide, means synchronizing movement of said slides, andautomatic means to' cause said slides to stop at apredeterminedposition. 2.1m a grinding machine, a grinding wheel, a

'steadyrest, a. slide to relatively advance the steadyrest relatively.to theaxis of a work piece,

feeding means `to move said slide, and means automatically to change therate of feed.

3. In a grinding-machine, agrinding wheel, 'a rotatable member to rotateawork'piece, means to relatively move the wheeland member, a steadyresthaving a. steadyrest suri'ace, -means to relatively move the steadyrestand lmein-,- ber, a plane of tangency at thecontact lsuriace makingr anacute angle to the direction of Emotion last specified, and `means tobring the steadyrest surface to a position a given tact with the workpiece, of means to move the grinding wheel, means to move the steadyrest elements, the grinding wheel and the steady rest surfaces being al1of them tangent to a given circle and the lines oi tangency for eachbeing on the circle more than 180 remote from one of the others in eachangular direction, the means to advance the grinding wheel and the meansto advance the steady rest elements being synchronized so that asgrinding proceeds the three elements are .maintained tangent to smallerand smaller circles all of which are concentric to the given circle,whereby to achieve accuracy in the' grinding of a work piece locatedconcentric withl the given circle.

5. In a grinding machine as claimed in claim 4 the combination with the'parts and features therein specified of driving means for the workpiece constituting a pair of pressure plates urged against it in opositedirections along the axis' of the given circle. l

6. In a grinding machine as claimed in claim 4 the combination with theparts and features therein specified of a rigid connection between th'etwo steady rest elements.

ADoLPH L. DE LEEUW.

